1 // reverse.h
2
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 // Copyright 2005-2010 Google, Inc.
16 // Author: riley@google.com (Michael Riley)
17 //
18 // \file
19 // Expand a PDT to an FST.
20
21 #ifndef FST_EXTENSIONS_PDT_REVERSE_H__
22 #define FST_EXTENSIONS_PDT_REVERSE_H__
23
24 #include <unordered_map>
25 using std::tr1::unordered_map;
26 using std::tr1::unordered_multimap;
27 #include <vector>
28 using std::vector;
29
30 #include <fst/mutable-fst.h>
31 #include <fst/relabel.h>
32 #include <fst/reverse.h>
33
34 namespace fst {
35
36 // Reverses a pushdown transducer (PDT) encoded as an FST.
37 template<class Arc, class RevArc>
Reverse(const Fst<Arc> & ifst,const vector<pair<typename Arc::Label,typename Arc::Label>> & parens,MutableFst<RevArc> * ofst)38 void Reverse(const Fst<Arc> &ifst,
39 const vector<pair<typename Arc::Label,
40 typename Arc::Label> > &parens,
41 MutableFst<RevArc> *ofst) {
42 typedef typename Arc::Label Label;
43
44 // Reverses FST
45 Reverse(ifst, ofst);
46
47 // Exchanges open and close parenthesis pairs
48 vector<pair<Label, Label> > relabel_pairs;
49 for (size_t i = 0; i < parens.size(); ++i) {
50 relabel_pairs.push_back(make_pair(parens[i].first, parens[i].second));
51 relabel_pairs.push_back(make_pair(parens[i].second, parens[i].first));
52 }
53 Relabel(ofst, relabel_pairs, relabel_pairs);
54 }
55
56 } // namespace fst
57
58 #endif // FST_EXTENSIONS_PDT_REVERSE_H__
59